1. Field of the Invention
The invention relates to a back-up tong of the type used in conjunction with a power tong to assemble or disassemble threaded joint connections between successive tubing sections that form the continuous tubing string extending through a well bore into underground deposits. More particularly this invention relates to a back-up tong that provides opposing reactive force to the torque of a power tong without rotating the back-up tong one-hundred eighty (180) degrees when the rotation of the power tong is reversed.
2. Related Art
To interconnect and disconnect tubing that is lowered into oil or gas production wells, two types of tongs are typically utilized to make or break the threaded joint connections between successive tubing sections. The ends of each tubing section are threaded with a male screw thread at one end and a female screw thread at an opposite end. As each tube section is lowered into the well bore, a successive section is screwed to its upper end. Power tongs apply torque to the upper tubing of the joint, while a back-up tong applies opposing torque to the lower tubing of the joint. In this manner, the back-up tong reacts against the torque applied by the power tong to the upper tubing of the joint, as such, the back-up tong keeps the bottom tubing of the joint from rotating when the power tong applies torque to the upper tubing to connect or disconnect threaded joint connections between tubing sections.
Today, power/back-up tong combination devices, such as the tong combination device 100 illustrated in prior art FIG. 1, are utilized to assemble and disassemble threaded joint connections between successive tubing sections that form the continuous tubing string extending through a well bore into underground deposits. As illustrated in FIG. 1, a back-up tong 102 is generally suspended from a power tong 104, so that the reaction torque of one tong is cancelled by the other tong, which eliminates the need to anchor the tongs to the oil rig. Instead, the tong combination device 100 is suspended by a hoist over the well bore. In such arrangements, the tail end 106 of the back-up tong 102 attaches to a structural support 108 on the back end of the power tong 104.
Current designs also feature a swivel and hinge mounting of the back-up tong 102 that allows the back-up tong 102 to be lowered away from the power tong 104 to permit rotation of the back-up tong 102 by one-hundred eighty (180) degrees in relation to the tubing being assembled. The jaws of current back-up tongs 102 only apply torque in one opposing rotational direction. To provide appropriate reactive force to the torque of the power tong 104, the back-up tong 102 must be flipped over according to the direction of rotation of the power tong 104. Accordingly, if rotation must be reversed, for example, from assembling tubing sections to disassembling the tubing sections, the power tong 104 and back-up tong 102 are removed from the tubing connection area and the power tong 104 is adjusted to perform the opposite rotation. The back-up tong 102 is then rotated upside down to react to the reversed torque of the power tong 104 on the tubing T.
An example of a current back-up tong 102 generally used in a power/back-up tong combination device 100, such as the device illustrated in FIG. 1, is described in U.S. Pat. No. 5,823,074 and illustrated in FIG. 2. FIG. 2 illustrates a top view of an open-head Foster-style back-up tong 200 having three pivoting jaws 202 in mesh connection with a ring gear 204. A drive cylinder 206 powered by a hydraulic motor engages the outer circumference of the ring gear 204. As illustrated in FIG. 3, rotation of the ring gear 204 in one direction causes each of the jaws 202 to pivot toward the center of the ring gear 204 and grip any tubing placed in the center opening of the back-up tong 200.
While the open-head Foster-style back-up tongs 200 work well, such back-up tongs still require more than one individual to operate. The current open-head Foster-style back-up tongs, of the type illustrated in FIGS. 2-3, only apply torque in one opposing rotational direction. Thus, current back-up tongs still require rotation to provide appropriate reactive force to the torque of the power tong when the rotation of the power tong is reversed.
Accordingly, a need exists for a back-up tong that can provide reactive force to the torque of the power tong when rotation of the power tong is reversed without requiring the back-up tong to be rotated one-hundred and eighty (180) degrees. In other words, a need exists for a back-up tong capable of gripping a pipe for assembling and disassembling pipe joints without rotating the back-up tong (i.e., reversing the back-up tong by turning the back-up tong upside down).